Hmmm, I'm surprised I never found this thread before. I'm a *huge* pandora.com fan and I used to listen to it pretty much every day. Now that I have a new work computer that has my iTunes library on it I don't listen to it quite as much, but I still do use it.
Pandora.com has pretty much been my main source for new music for the last 1 1/2 years. Almost all of my CD purchases and trades have been to get music I first heard on Pandora.
Then thing I like most about Pandora is that it gets me to listen to things I wouldn't have even considered trying before. So I actually have acquired some guilty pleasure songs from people I wouldn't have even given a listen before. It's also opened me up to a slew of artists I'd never heard of before and wasn't likely to hear about any other way.
I don't really listen to the radio much and I don't watch much music TV, so pandora is my main source for new sounds.